Return false on wlr_keyboard_set_keymap() failure

This allows users of the library to handle or ignore the error as they
see fit.

include/wlr/types/wlr_keyboard.h

@@ -103,7 +103,7 @@ struct wlr_event_keyboard_key {
 	enum wlr_key_state state;
 };
 
-void wlr_keyboard_set_keymap(struct wlr_keyboard *kb,
+bool wlr_keyboard_set_keymap(struct wlr_keyboard *kb,
 	struct xkb_keymap *keymap);
 /**
  * Sets the keyboard repeat info. `rate` is in key repeats/second and delay is

types/wlr_keyboard.c

@@ -145,7 +145,7 @@ void wlr_keyboard_led_update(struct wlr_keyboard *kb, uint32_t leds) {
 	}
 }
 
-void wlr_keyboard_set_keymap(struct wlr_keyboard *kb,
+bool wlr_keyboard_set_keymap(struct wlr_keyboard *kb,
 		struct xkb_keymap *keymap) {
 	xkb_keymap_unref(kb->keymap);
 	kb->keymap = xkb_keymap_ref(keymap);
@@ -199,7 +199,7 @@ void wlr_keyboard_set_keymap(struct wlr_keyboard *kb,
 	keyboard_modifier_update(kb);
 
 	wlr_signal_emit_safe(&kb->events.keymap, kb);
-	return;
+	return true;
 
 err:
 	xkb_state_unref(kb->xkb_state);
@@ -208,6 +208,7 @@ err:
 	kb->keymap = NULL;
 	free(kb->keymap_string);
 	kb->keymap_string = NULL;
+	return false;
 }
 
 void wlr_keyboard_set_repeat_info(struct wlr_keyboard *kb, int32_t rate,